This application is based on application No. 2000-160032 filed in Japan, the content of which is hereby incorporated by reference.
(1) Field of the Invention
The present invention relates to a map display device, a map display method, and a computer program for use in a map display device, and in particular relates to road map display techniques used in car navigation devices.
(2) Related Art
Example applications for map display devices include a car navigation device. A map display device used in a car navigation device needs to enable the user, such as the driver, to comprehend a displayed map at a glance. Hence various map display techniques have been devised so that the driver can understand information at once. One of such techniques is a method of displaying with emphasis on information which is likely to be desired by the driver.
When driving a car, there are some points to which the driver seems to pay particular attention, such as an intersection and a destination location. Such points are hereinafter called xe2x80x9cpoints of interestxe2x80x9d. A conventional type of map display device displays an enlarged view of a point of interest and its vicinity. For example, when a car is approaching a main intersection, this type of map display device displays an enlarged view of the intersection and its vicinity, to help the driver judge which route he or she should take. Here, some map display devices display the enlarged view over a part of a map which is being displayed on a screen, rather than displaying the enlarged view on the whole screen.
Also, there are map display devices that display, over a part of a map which is being displayed on a screen, a wide area view of the periphery of an area covered by the map on a larger scale. This method allows the driver to consult the map, and at the same time consult the wide area view to check which roads run around the area covered by the map.
Thus, conventional map display devices emphasize information which is likely to be desired by the driver, by displaying an enlarged view of the vicinity of a point of interest or a wide area view of the periphery of an area shown by a map. In this way, the driver can quickly comprehend information displayed on the screen.
However, when displaying the enlarged view of the vicinity of the point of interest on the whole screen, the driver can view the enlarged view but cannot view the map of the area outside the vicinity of the point of interest, and therefore cannot check the roads existing around the vicinity of the point of interest.
Also, when displaying the enlarged view of the vicinity of the point of interest or the wide area view of the periphery of the area covered by the map on part of the screen, the driver cannot view the part of the map which is concealed by this display. Besides, there is no continuity between the map and the enlarged or wide area view whose scale is different with the map. This makes it difficult for the driver to quickly comprehend the relation between the two maps, in particular connections of roads between the two maps.
There is also a conventional technique of displaying a map using the law of perspective. This method displays distant objects to be small and close objects to be large in accordance with human visual characteristics, thereby helping the driver view the map in the right perspective. However, when displaying the vicinity of a point of interest in enlarged view or displaying the periphery of an area in wide area view, this technique has the same problem as above.
The present invention has an object of providing a map display device that enables a driver to accurately and quickly comprehend map information displayed on a display screen.
(1) The stated object can be achieved by a map display device that is characterized by mapping a map of an area which is specified by a current position of the map display device or by an instruction from a user, onto a curved surface to generate a mapped image, and displaying the mapped image.
With this construction, the map display device can display a map with one or more portions enlarged and/or contracted, while maintaining connections of roads. For instance, it is possible to enlarge a map portion the detailed information of which is likely to be desired by the driver, and at the same time contract a map portion of the periphery of the map so that the periphery is displayed in wide area view. As a result, the connections of the roads are maintained, and the driver can accurately and quickly comprehend the map information displayed on the display screen.
(2) Here, in the map display device of (1), the map has at least one portion which is to be enlarged and/or at least one portion which is to be contracted, the portion to be enlarged and the portion to be contracted being referred to as an enlarged portion and a contracted portion respectively, and the curved surface has a form which depends on a positioning of the enlarged portion and/or the contracted portion on the map.
With this construction, the map display device produces the same effect as (1).
(3) Here, the map display device of (2) includes: a map storing unit for storing map information; a map acquiring unit for acquiring map information that shows the map of the area specified by the current position of the map display device, from the map storing unit; a surface storing unit for storing surface information that defines the curved surface whose form depends on the positioning of the enlarged portion and/or the contracted portion on the map shown by the acquired map information; a mapping unit for mapping the map shown by the acquired map information, onto the curved surface defined by the surface information, to generate the mapped image; and a projecting/displaying unit for projecting the mapped image onto a flat virtual screen, and displaying the projected image.
With this construction, the map display device produces the same effect as (1).
(4) Here, in the map display device of (3), the curved surface defined by the surface information has the following property: when the map is mapped onto the curved surface by the mapping unit and projected onto the virtual screen by the projecting/displaying unit, (a) an angle formed between a part of the curved surface to which the enlarged portion of the map is mapped and a line of sight directed to the part of the curved surface in the projection is larger than any angles formed between other parts of the curved surface and lines of sight directed to the other parts of the curved surface in the projection, and (b) an angle formed between a part of the curved surface to which the contracted portion of the map is mapped and a line of sight directed to the part of the curved surface in the projection is smaller than any angles formed between other parts of the curved surface and lines of sight directed to the other parts of the curved surface in the projection.
With this construction, the map display device produces the same effect as (1).
(5) Here, the map display device of (4) further includes an altitude storing unit for storing altitude information showing a correspondence between positions of points shown in the map and altitudes of the points, wherein the mapping unit includes a surface deforming unit for providing undulations corresponding to the altitudes shown by the altitude information, to the curved surface at positions to which the points on the map at the corresponding positions shown by the altitude information are to be mapped, to generate a deformed curved surface, and the mapping unit maps the map onto the deformed curved surface.
With this construction, the map display device displays the map of three-dimensional appearance relating to the altitudes, so that the map which delivers the same degree of realism as the view when looking at the actual terrain from the sky can be presented to the driver. Accordingly, in addition to the effect of (1), the driver""s understanding of the terrain is facilitated.
(6) Here, in the map display device of (5), the surface deforming unit includes an altitude changing unit for changing altitudes in the altitude information that correspond to positions included in a first area which is made up of the current position of the map display device in the map and a neighborhood thereof, to a uniform value, and the surface deforming unit generates the deformed curved surface, using the changed altitude information.
With this construction, the map display device displays the vicinity of the car position flatly and the other area three-dimensionally. Accordingly, in addition to the effect of (5), the display of the vicinity of the car position is kept from being obstructed by the undulations.
(7) Here, in the map display device of (6), the altitude changing unit further changes altitudes in the altitude information that correspond to positions included in an area around the first area, in accordance with distances of the positions from the first area.
With this construction, the map display device displays the boundary area between the flatly displayed area and the three-dimensionally displayed area so that the flat area and the three-dimensional area show continuity. Accordingly, in addition to the effect of (6), unnaturalness in visuality is reduced.
(8) Here, the map display device of (3) further includes a surface receiving unit for receiving the surface information, wherein the surface storing unit stores the surface information received by the surface receiving unit.
With this construction, when a position of a point of interest changes in a complex manner as the car moves, a surface calculating device provided outside the map display device calculates surface information for enlarging and/or contracting desired portions of the map and supplies it to the map display device. As a result, the load of computation is distributed over the two devices, and the map display is performed more smoothly.
(9) Here, in the map display device of (3), the projecting/displaying unit includes a projection position storing unit for storing a correspondence between positions on the curved surface and positions on the virtual screen to which points at the positions on the curved surface are to be projected.
With this construction, the map display device calculates and stores projection positions on the virtual screen in advance. This makes it unnecessary to calculate the projection positions which requires large computational complexity, for each projection operation. As a result, the map display speed is improved.
(10) Here, in the map display device of (3), the map information stored in the map storing unit includes (a) image information showing an image in which graphics representative of objects are drawn in correspondence with positions of the objects on the ground surface, and (b) character information showing a correspondence between character strings relating to the objects and the positions of the objects on the ground surface, the map acquiring unit acquires image information and character information which relate to the map of the area specified by the current position of the map display device, from the map storing unit, the map display device further includes a character display position calculating unit for calculating points on the curved surface to which points on the map at positions shown by the acquired character information are mapped, and calculating positions on the virtual screen to which the calculated points on the curved surface are projected, the mapping unit maps an image shown by the acquired image information to generate the mapped image, and the projecting/displaying unit further displays character strings shown by the acquired character information with reference to the calculated positions.
With this construction, the map display device does not subject the character fonts to mapping and perspective projection, but directly displays the character fonts at the position on the display screen corresponding to the character position. As a result, the deformation of the character fonts which may occur due to mapping and perspective projection is avoided, and the character viewability is increased.
(11) Here, the map display device of (3) is mounted on a movable body, and further includes a positional information receiving unit for receiving positional information showing a current position and a traveling direction of the movable body, wherein the map acquiring unit acquires the map information showing the map of the area specified by the positional information received by the positional information receiving unit, from the map storing unit.
With this construction, when the map display device is mounted on a movable body and used, a map of an appropriate area is displayed in accordance with the current position and traveling direction of the movable body.
(12) Here, the map display device of (11) further includes a map receiving unit for receiving map information transmitted by radio, wherein the map storing unit stores the map information received by the map receiving unit.
With this construction, the map display device displays latest map information transmitted by radio. Accordingly, a map that contains information on latest road conditions such as the closure and opening of roads can be presented to the driver.
(13) Here, the map display device of (2) includes: a map storing unit for storing map information; a map acquiring unit for acquiring map information that shows the map of the area specified by the current position of the map display device, from the map storing unit; a surface storing unit for storing surface information that defines a virtual screen having the form of the curved surface which depends on the positioning of the enlarged portion and/or the contracted portion on the map shown by the acquired map information; and a projecting/displaying unit for projecting the map shown by the acquired map information onto the virtual screen defined by the surface information, and displaying a projected image obtained as a result of the projection.
With this construction, the map display device produces the same effect as (1).
(14) Here, in the map display device of (13), the virtual screen defined by the surface information has the following property: when the map is projected onto the virtual screen by the projecting/displaying unit, (a) an angle formed between a part of the virtual screen to which the enlarged portion of the map is projected and a line of sight directed to the part of the virtual screen in the projection is smaller than any angles formed between other parts of the virtual screen and lines of sight directed to the other parts of the virtual screen in the projection, and (b) an angle formed between a part of the virtual screen to which the contracted portion of the map is projected and a line of sight directed to the part of the virtual screen in the projection is larger than any angles formed between other parts of the virtual screen and lines of sight directed to the other parts of the virtual screen in the projection.
With this construction, the map display device produces the same effect as (1).
(15) Here, the map display device of (14) further includes an altitude storing unit for storing altitude information showing a correspondence between positions of points shown in the map and altitudes of the points, wherein the projecting/displaying unit includes a map deforming unit for providing undulations corresponding to the altitudes shown by the altitude information, to the map at the corresponding positions shown by the altitude information, to generate a deformed map, and the projecting/displaying unit projects the deformed map onto the virtual screen.
With this construction, the map display device displays the map of three-dimensional appearance relating to the altitudes, so that the map which delivers the same degree of realism as the view when looking at the actual terrain from the sky can be presented to the driver. Accordingly, in addition to the effect of (1), the driver""s understanding of the terrain is facilitated.
(16) Here, in the map display device of (15), the map deforming unit includes an altitude changing unit for changing altitudes in the altitude information that correspond to positions included in a first area which is made up of the current position of the map display device in the map and a neighborhood thereof, to a uniform value, and the map deforming unit generates the deformed map, using the changed altitude information.
With this construction, the map display device displays the vicinity of the car position flatly and the other area three-dimensionally. Accordingly, in addition to the effect of (15), the display of the vicinity of the car position is kept from being obstructed by the undulations.
(17) Here, in the map display device of (16), the altitude changing unit further changes altitudes in the altitude information that correspond to positions included in an area around the first area, in accordance with distances of the positions from the first area.
With this construction, the map display device displays the boundary area between the flatly displayed area and the three-dimensionally displayed area so that the flat area and the three-dimensional area show continuity. Accordingly, in addition to the effect of (16), unnaturalness in visuality is reduced.
(18) Here, the map display device of (13) further includes a surface receiving unit for receiving the surface information, wherein the surface storing unit stores the surface information received by the surface receiving unit.
With this construction, when a position of a point of interest changes in a complex manner as the car moves, a surface calculating device provided outside the map display device calculates surface information for enlarging and/or contracting desired portions of the map and supplies it to the map display device. As a result, the load of computation is distributed over the two devices, and the map display is performed more smoothly.
(19) Here, in the map display device of (13), the projecting/displaying unit includes a projection position storing unit for storing a correspondence between positions on the map and positions on the virtual screen to which points at the positions on the map are to be projected.
With this construction, the map display device calculates and stores projection positions on the virtual screen in advance. This makes it unnecessary to calculate the projection positions which requires large computational complexity, for each projection operation. As a result, the map display speed is improved.
(20) Here, in the map display device of (13), the map information stored in the map storing unit includes (a) image information showing an image in which graphics representative of objects are drawn in correspondence with positions of the objects on the ground surface, and (b) character information showing a correspondence between character strings relating to the objects and the positions of the objects on the ground surface, the map acquiring unit acquires image information and character information which relate to the map of the area specified by the current position of the map display device, from the map storing unit, the map display device further includes a character display position calculating unit for calculating positions on the virtual screen to which points on the map at positions shown by the acquired character information are to be projected, and the projecting/displaying unit projects an image shown by the acquired image information to generate the projected image, and displays character strings shown by the acquired character information with reference to the calculated positions.
With this construction, the map display device does not subject the character fonts to mapping and perspective projection, but directly displays the character fonts at the position on the display screen corresponding to the character position. As a result, the deformation of the character fonts which may occur due to mapping and perspective projection is avoided, and the character viewability is increased.
(21) Here, the map display device of (13) is mounted on a movable body, and further includes a positional information receiving unit for receiving positional information showing a current position and a traveling direction of the movable body, wherein the map acquiring unit acquires the map information showing the map of the area specified by the positional information received by the positional information receiving means, from the map storing unit.
With this construction, when the map display device is mounted on a movable body and used, a map of an appropriate area is displayed in accordance with the current position and traveling direction of the movable body.
(22) Here, the map display device of (21) further includes a map receiving unit for receiving map information transmitted by radio, wherein the map storing unit stores the map information received by the map receiving unit.
With this construction, the map display device displays latest map information transmitted by radio. Accordingly, a map that contains information on latest road conditions such as the closure and opening of roads can be presented to the driver.
(23) The stated object can also be achieved by a map display method for use in a map display device for displaying a map with one or more portions enlarged and/or contracted, including: a map receiving step for receiving map information that shows a map of an area specified by a current position of the map display device, wherein surface information that defines a curved surface whose form depends on a positioning of one or more portions to be enlarged and/or contracted on the map shown by the map information is stored in a storing unit in the map display device; a mapping step for mapping the map shown by the map information, onto the curved surface defined by the surface information, to generate a mapped image; and a projecting/displaying step for projecting the mapped image onto a flat virtual screen, and displaying the projected image.
With this construction, the map display operation that has the same effect as (1) can be performed.
(24) The stated object can also be achieved by a map display method for use in a map display device for displaying a map with one or more portions enlarged and/or contracted, including: a map receiving step for receiving map information that shows a map of an area specified by a current position of the map display device, wherein surface information that defines a virtual screen having a form of a curved surface which depends on a positioning of one or more portions to be enlarged and/or contracted on the map shown by the map information is stored in a storing unit in the map display device; and a projecting/displaying step for projecting the map shown by the map information onto the virtual screen defined by the surface information, and displaying a projected image obtained as a result of the projection.
With this construction, the map display operation that has the same effect as (1) can be performed.
(25) The stated object can also be achieved by a computer program recorded on a computer-readable recording medium, for use in a map display device that displays a map with one or more portions enlarged and/or contracted, the program including: a map receiving step for receiving map information that shows a map of an area specified by a current position of the map display device, wherein surface information that defines a curved surface whose form depends on a positioning of one or more portions to be enlarged and/or contracted on the map shown by the map information is stored in a storing unit in the map display device; a mapping step for mapping the map shown by the map information, onto the curved surface defined by the surface information, to generate a mapped image; and a projecting/displaying step for projecting the mapped image onto a flat virtual screen, and displaying the projected image.
With this construction, the map display operation that has the same effect as (1) can be executed on computer.
(26) The stated object can also be achieved by a computer program recorded on a computer-readable recording medium, for use in a map display device that displays a map with one or more portions enlarged and/or contracted, the program including: a map receiving step for receiving map information that shows a map of an area specified by a current position of the map display device, wherein surface information that defines a virtual screen having a form of a curved surface which depends on a positioning of one or more portions to be enlarged and/or contracted on the map shown by the map information is stored in a storing unit in the map display device; and a projecting/displaying step for projecting the map shown by the map information onto the virtual screen defined by the surface information, and displaying a projected image obtained as a result of the projection.
With this construction, the map display operation that has the same effect as (1) can be executed on computer.